Modern vehicles often incorporate one or more drivetrain modes for providing power from an engine to the driven wheels. For example, a vehicle with only a two-wheel drive system, or 4×2 mode, may provide power via one or a series of rotating shafts to two wheels of the vehicle. Vehicles such as compact cars may use a front wheel drive system with power provided to the two front wheels. In other, often larger vehicles, it is often desirable to incorporate both two-wheel drive and four-wheel drive driving modes, wherein power may be selectively distributed to two wheels in one mode and four wheels in another mode. Vehicles of different sizes often incorporate two-wheel drive of the rear wheels and four-wheel drive for the purpose of enabling better handling during varying traction conditions while still being able to switch to two-wheel drive to reduce fuel consumption and reduce wasted power.
For vehicles with switchable drive modes, devices and systems are needed for engaging and disengaging drivetrain components such as axles and shafts. As such, disconnect assemblies are used that often involve a form of clutch that can move to connect or disconnect two rotatable components such as two shafts. The disconnect assemblies can be placed in a variety of areas in the drivetrain of a vehicle, including at the wheel ends, at one or more axles, or along one of the drive shafts. Through the use of disconnect systems, vehicles can be made more versatile by having the ability to switch between different drive modes depending on the driving conditions and operator desire.
In some powertrain disconnecting systems, vacuum directed from the vehicle engine is used as the motive or actuating force that powers the disconnecting systems. In particular, the disconnecting system actuators may be powered by the vacuum. In many systems, the vacuum is directed via a passage from the intake manifold of the gasoline-fueled engine. Due to this, the vacuum level, or amount of force or pressure available from the vacuum, may vary as engine throttle settings change along with engine load. For many engine systems, the vacuum level (amount of pressure available) may be limited or vary due to the effects of altitude. Furthermore, temperature changes can also cause pressure fluctuations in the vacuum level, thereby causing fluctuations in movement of the disconnect actuator which may result in undesirable movement of disconnect components such as the diaphragm and clutch components. Additionally, in some vehicles vacuum may not be readily available since various vehicle accessory systems may not be powered by vacuum, or the vehicle may be designed to remove engine intake connections such as vacuum lines in order to enhance engine control and performance. Finally, vacuum-powered powertrain disconnect systems are becoming less desirable with more advanced vehicle design. As such, powertrain disconnect systems are needed that are powered by sources other than vacuum and feature designs conducive to modern vehicle systems. The inventors herein have recognized the above issues and developed various approaches to address them.
Thus in one example, the above issues associated with vacuum powered disconnects may be at least partially addressed by a method of operating a disconnect assembly of a shaft, comprising: driving a shifter mechanism from a first self-locking position to a second self-locking position via an electromagnetic coil generating an axial force through an armature cam assembly including a series of bi-directional ramps interfacing with axially extending guides of the shifter mechanism, the coil energized only during transitions between the first and second self-locking positions, the first and second self-locking positions including a shaft engaging position and a shaft disengaging position. In this way, a compact disconnect assembly is provided that is powered by discrete pulses of electrical current to an electromagnetic coil located in the disconnect assembly, while not relying on vacuum power. The electromagnetic coil may be designed to only come into contact with an armature of the disconnect assembly when the coil is energized or activated, thereby increasing the longevity of the contacting components.
The electromagnetic pulse disconnect assembly may also include a magnetic position sensor assembly to monitor the position of the moving components of the assembly that allow for switching between different driving modes, such as four-wheel drive and two-wheel drive. The sensor assembly may be configured to detect the strength of a magnetic field produced by a magnet located on a translating but non-rotating component of the disconnect assembly. Correlating the magnetic field strength with position of the disconnect assembly may allow for accurate monitoring of the shifting motions of the disconnect assembly. Furthermore, by using a magnetic sensor, a space may be maintained such that the sensor does not interfere with the movement of the disconnect assembly.
The proposed electromagnetic disconnect assembly may alleviate the issues associated with vacuum-powered disconnects. By providing pulses of current from a power source, the disconnect assembly may consume less power than other disconnects that provide continuous current to enable shifting and maintain shifting positions. The current pulses may energize the electromagnetic coil to slow down rotation of the armature, thereby causing a ramping ring to translate in an axial direction to move a clutch ring in the same direction. As explained later, this movement along with a biasing engagement spring force may cause coupling and decoupling between two rotating components, such as drive shafts and/or axles.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.